1. Field of the Invention
The present invention relates to a semiconductor laser device structure, a thermally assisted magnetic head, and a method of manufacturing the same.
2. Related Background Art
As hard disk dives have been increasing their recording density, thin-film magnetic heads have been required to further improve their performances. As the thin-film magnetic heads, those of composite type having a structure in which a magnetic detecting device such as magnetoresistive (MR) device and a magnetic recording device such as electromagnetic coil device are laminated have been in wide use, while these devices read/write data signals from/onto magnetic disks which are magnetic recording media.
In general, a magnetic recording medium is a sort of discontinuous body in which magnetic fine particles are assembled, while each magnetic fine particle has a single-domain structure. Here, one recording bit is constituted by a plurality of magnetic fine particles. Therefore, for enhancing the recording density, it is necessary to make the magnetic fine particles smaller, so as to reduce irregularities at boundaries of recording bits. When the magnetic fine particles are made smaller, however, their volume decreases, so that the thermal stability in magnetization may deteriorate, thereby causing a problem.
An index of the thermal stability in magnetization is given by KUV/kBT. Here, KU is the magnetic anisotropy energy of the magnetic fine particle, V is the volume of one magnetic fine particle, kB is the Boltzmann constant, and T is the absolute temperature. Making the magnetic fine particles smaller just reduces V, thereby lowering KUV/kBT by itself, which worsens the thermal stability. Though KU may be made greater at the same time as measures against this problem, the increase in KU enhances the coercivity of the recording medium. On the other hand, the writing magnetic field intensity caused by a magnetic head is substantially determined by the saturated magnetic flux density of a soft magnetic material constituting a magnetic pole within the head. Therefore, no writing can be made if the coercivity exceeds a permissible value determined by the limit of writing magnetic field intensity.
Proposed as a method for solving such a problem in thermal stability of magnetization is a so-called thermally assisted magnetic recording scheme which applies heat to a magnetic recording medium immediately before applying a writing magnetic field, while using a magnetic material having a large value of KU, so as to effect writing with lowered coercivity. This scheme is roughly classified into magnetic dominant recording and optical dominant recording. In the magnetic dominant recording, the writing is attributed to an electromagnetic coil device, while the radiation diameter of light is greater than the track width (recording width). In the optical dominant recording, in contrast, the writing is attributed to a light-radiating part, while the radiation diameter of light is substantially the same as the track width (recording width). Namely, the magnetic dominant recording and optical dominant recording impart space resolution to a magnetic field and light, respectively.
Meanwhile, near-field probes (plasmon antenna) are disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-255254) and Patent Document 2 (Japanese Patent Application Laid-Open No. 2003-114184), for example. Patent Document 1 arranges a near-field probe so as to make it oppose a phase-change medium, while Patent Document 2 states that it is applicable to optical recording. These documents arrange a conductive planar near-field-light-generating part on a medium-opposing surface (Air Bearing Surface). Patent Document 3 (Japanese Patent Application Laid-Open No. 2006-185548) discloses a thermally assisted magnetic head which irradiates a magnetic recording medium with laser light through an optical waveguide. The laser light is emitted from a semiconductor laser device. Magnetic recording can also be performed while directly irradiating the medium with the light from the semiconductor laser device.
In any case, it will be preferred in a laser device structure using a semiconductor laser device such as the one mentioned above to physically secure the semiconductor laser device and a slider including the optical waveguide to each other, so as to keep the semiconductor laser device and the core of the optical waveguide from being misaligned in terms of their optical coupling relationship.